The Characteristics of Life

I. History A. Spontaneous Generation or Abiogenesis 1. 1 st proposed by Aristotle 2. Believed that complex, living organisms are generated by decaying organic substances, Ex. 1. that mice would spontaneously appear in stored grain or 2. maggots spontaneously appear in meat.

The Characteristics of Life I. History A.Spontaneous Generation or Abiogenesis 3. Was widely believed until the 19 th century. 4. Several scientists performed experiments that disproved spontaneous generation Francisco Redi Lazzaro Spallanzani Louis Pasteur

Pasteur’s Experiment Louis Pasteur 1859

I. The Characteristics of Life B. Biogenesis 1. The process of life forms producing life forms of the same kind Ex. a spider lays eggs, which hatch into spiders 2. The term is also used for the assertion that life can only be passed on by living things

I. The Characteristics of Life How can you tell if something is alive?

The Characteristics of Life Interesting Fact: Biologists have devised a list of 5 characteristics that define life. Interesting Fact: Something can be considered alive ONLY if it displays ALL 5 of the characteristics

The Characteristics of Life Anything that possesses all 5 of the characteristics of life is called an organism.

II. The 5 Characteristics of Life A. Cellular Organization cell  tissue  organ  system  organism B. Growth & Development C. Reproduction D. Adaptation to Environment E. Maintenance of Homeostasis

I. The 5 Characteristics of Life A. Cellular Organization - “All living forms of life are made up of cells and become more organized from this basic unit of life” Ex.-Cells form tissues -Tissues form organs -Organs form organ systems

I. The 5 characteristics of life Does it grow? Growth – an increase in the # of cells making up an organism increases it’s size Does it develop? Development – as cell #’s increase, they begin to diversify causing changes to take place throughout the the life span of the organism B. Growth & Development

I. The 5 Characteristics of Life C. Reproduction All living organisms are able to reproduce themselves Even one cell organisms replicate themselves

I. The 5 Characteristics of Life D. Adaptation to Environment All living organisms are able to adapt to their surroundings. “to adapt” -- to be able to react or respond - to something in the environment - to a “stimulus”

I. The 5 Characteristics of Life E. Maintain Homeostasis All living organisms are able to maintain a relatively constant internal environment that is suitable for it’s life Homeostasis - ? “homo” + “static”

The Characteristics of Life An Amazing Fact: THE HUMAN BODY –A collection of a trillion, diverse and highly organized cells –Whatever it takes to keep this collection of a trillion cells “alive” = what it takes for you and I to stay alive! WELCOME TO 21 ST CENTURY H.S. BIOLOGY! A year of study to answer this question: What DOES IT TAKE to keep cells alive?